Hydrogenation of 1,3,7-octatriene to 1,6-octadiene and 1,5-octadiene with certain chromium carbonyl catalysts

ABSTRACT

1,3,7-Octatriene, which can be made by the dimerization of butadiene, can be selectively hydrogenated to 1,5-octadiene and 1,6-octadiene in the presence of a chromium carbonyl catalyst such as chromium hexacarbonyl, pentacarbonyl( phosphine) chromium and tricarbonyl(arene)chromium complexes. Isomer distribution in the product can be modified by the presence of carbon monoxide. The diene products are useful comonomers for addition copolymers such as ethylene propylene/diene elastomeric copolymers, the diene-derived units forming crosslinking sites for any of the elastomers with conventional sulfur curing systems.

United States Patent Gosser [54] HYDROGENATION OF 1,3,7-

OCTATRIENE TO 1,6-OCTADIENE AND 1,5-OCTADIENE WITH CERTAIN CHROMIUM CARBONYL CATALYSTS [72] Inventor: Lawrence Wayne (,osser, Wilmington,

Del.

[73] Assigncc: I. du Pont de Nemours and Company,

Wilmington, Del.

[22] Filed: Dec. 11, 1970 [2]] Appl. No.: 97,315

[52] US. Cl. ..260/680 R, 260/4385 R, 260/677 R [51] lnt.Cl ..C07c 5/16,C07c ll/l2 [58] Field of Search ..260/680 R, 683.9, 438.5 R, 260/666 B, 677 H [56] References Cited UNITED STATES PATENTS 6/1964 Ecke ..260/438.5 X

Kittleman et al. ..260/666 Whiting ..260/438.5 X

Primary Examiner-Paul M. Coughlan, Jr. Attorney-D. R. J. Boyd (57] ABSTRACT l,3,7-Octatriene, which can be made by the dimerization of butadiene, can be selectively hydrogenated to l,5-octadiene and l,6-octadiene in the presence of a chromium carbonyl catalyst such as chromium hexacarbonyl, pentacarbonyl( phosphine) chromium and tricarbonyl(arene)chromium complexes. isomer distribution in the product can be modified by the presence of carbon monoxide. The diene products are useful comonomers for addition copolymers such as ethylene propylene/diene elastomeric copolymers, the diene-derived units forming crosslinking sites for any of the elastomers with conventional sulfur curing systems.

l0 Claims, No Drawings I-IYDROGENATION OF 1,3,7-OCTATRIENE TO 1,6- OCTADIENE AND 1,5-OCTADIENE WITH CERTAIN CHROMIUM CARBONYL CATALYSTS FIELD OF THE INVENTION This invention relates to the selective hydrogenation of 1,3,7-octatriene to 1,5-octadiene and 1,6-ctadiene.

PRIOR ART Tricarbonyl(arene)chromium complexes are known to be catalysts for hydrogenation and isomerization of diene functions in carboxylic acid derivatives. Frankel et al. [Tetrahedron Letters, No. 16, pp. l9l9l923 (1968)] have shown that conjugated diene or triene units in fatty acid esters such as methyl sorbate and methyl ,B-eleostearate are hydrogenated to corresponding monoene or non-conjugated diene units in the presence of tricarbonyl(methyl benzoate)chromium and similar tricarbonyl(arene)chromium complexes. They also disclose that non-conjugated diene units in the reaction mixtures are not reduced. Rejoan et al. [Proceedings of the Eleventh Coordination Chemistry Conference, Elsevier Publishing Co., New York (1968)] disclose chromium hexacarbonyl as a catalyst for hydrogenation of methyl sorbate to methyl 3-hexenoate.

SUMMARY OF THE INVENTION The reaction of this invention is summarized by the following:

the hydrogenation being conducted in the presence of a catalytic amount of neutral chromium complex having at least three carbonyl ligands attached to each chromium atom, at a temperature of 25 to 300 C. and in the presence of hydrogen at a partial pressure of about 1 to about l ,000 atmospheres.

DETAILED DESCRIPTION OF THE INVENTION The process of this invention is carried out conventionally by heating a mixture of 1,3,7-octatriene and the chromium carbonyl catalyst, with or without added solvent, under hydrogen in a pressure vessel. Carbon monoxide can be present in the gaseous phase if desired. The liquid reaction mixture is cooled and removed from the reactor after the pressure of hydrogen and any carbon monoxide is released. Hydrocarbon components of the reaction mixture are collected by distillation, and can be separated by conventional means such as fractional distillation.

In this reaction, 1,5- and 1,6-octadienes are the major products, the l,6-isomer normally being predominant. Side reactions also lead to small amounts of other hydrocarbon products such as 1,3,6-octatriene, 1,3- and 2,6-octadienes, isomeric octenes and octane. The 1,6-octadiene product is essentially all in the cis stereoisomeric form, and the 1,5-octadiene is mainly in the cis form but may contain as much as 30 percent of the trans stereoisomer.

The chromium carbonyl complexes which are effective catalysts in the process of this invention are chromium hexacarbonyl, pentacarbonyl( trisubstituted phosphine )chromium compounds, and tricarbonyl(arene)chromium complexes.

The pentacarbonyl(trisubstituted phosphine)chromium complexes have the formula 3 )5 wherein each L can be alike or different and consists of a hydrocarbyl group free of aliphatic unsaturation or an aryl group containing saturated hydrocarbon, lower alkoxy and halogen substituents and having up to 10 carbon atoms in the molecule.

A hydrocarbyl group is a group derived from a hydrocarbon by removal of an atom of hydrogen. Hydrocarbyl groups free of aliphatic unsaturation therefore include radicals derived from saturated hydrocarbons such as alkyl radicals, cycloalkyl radicals and bridged cycloalkyl radicals, and radicals derived from aromatic hydrocarbons containing one or more benzene rings which may be condensed, and which contain only saturated hydrocarbon substituents. Radicals derived from aromatic hydrocarbons can be classified according to whether they are formed by removal of a hydrogen from an aromatic nucleus (which are called aryl radicals), or, when the aromatic hydrocarbon contains one or more saturated hydrocarbon substituents, by removal of a hydrogen atom from a saturated carbon atom (which are called aralkyl substituents). Examples of suitable hydrocarbyl radicals include: methyl, ethyl, npropyl, isopropyl, n-butyl, t-butyl, 2-ethylhexyl, n-octyl, 2- methyloctyl, cyclopentyl, cyclohexyl, 4-ethylcyclohexyl, benzyl, 4-methylbenzyl, 3,4-dimethylbenzyl, phenyl, tolyl, 2,4-dimethylphenyl and the like. Triaryl phosphines, especially triphenyl phosphines, are preferred.

Examples of aryl radicals containing halogen or alkoxy substituents include 4-fluorophenyl, 4-chlorophenyl, 4- bromophenyl, 4-iodophenyl, 3-chlorophenyl, 3-chloro-4- methylphenyl, 3-propyl-4-fluorophenyl, 3,5-dimethyl-4- bromophenyl, 4-methoxyphenyl, 4-ethoxyphenyl, 3-methoxy- 4-methylphenyl and the like.

Tricarbonyl(arene)chromium compounds have the general formula:

where Q is an aromatic compound which can contain up to 14 carbon atoms and can be benzene, toluene, o-, m-, or pxylene, ethylbenzene, mesitylene, hexamethylbenzene, pcymene, isopropylbenzene, l ,3 -di( t-butyl )benzene, naphthalene, tetralin, anthracene, phenanthrene, biphenyl, diphenylmethane, 1,2-diphenylethylene, 1,4-diphenylbutadiene, indane, ffluorene and the like or such hydrocarbon with up to 3 substituents which can be lower alkoxy (OR), lower alkanecarbonyloxy (OCOR), lower alkoxycarbonyl (COOR), lower alkoxycarbonylalkyl (RCOOR), hydroxymethyl (.;CH OH), cyano (CN), lower alkylcarbonyl (-COR), arylcarbonyl (COAr), amino (NH N- (lower alkyl)amino'alkyl)amino (NHR), N,N-di(lower alkyl)amino alkyl)amino (NR halogen and the like.

Examples of substituted aromatic hydrocarbons include fluorobenzene, chlorobenzene, anisole, ethyl phenylacetate, methyl benzoate, 2,5-dimethoxy-1,4-di-(t-butyl)benzene, benzophenone, aniline, toluidine, N-methylaniline, N,N- dimethyltoluidine, benzyl alcohol, and the like. i V

The chromium. carbonyl catalysts are normally used in a g. catalyst/ml triene ratio in the range of 0.001 to 1.0, and the ratio in the range of about 0.01 to about 0.2 is preferred.

The reaction can be run without an added solvent, i.e., neat or in the presence of an inert solvent such as hexane, cyclohexane, or acetone. When a solvent is used, it is recommended that the proportions of solvent and catalyst are adjusted so that the catalyst concentration in the reaction mixture, including both solvent and triene, is within the range of 0.0005 to 1 g/ml, and preferably in the range of 0.01 to 0.05 g/ml. It is also preferred to limit the solvent to an amount which allows a triene concentration of at least 10 percent in the initial reaction mixture. Inert nonpolar solvents such as hexane have negligible effects on the rate of reaction, while inert polar solvents such as acetone generally enhance the rate of reaction and may also effect changes in the relative proporgenerally results in a reduced rate of hydrogenation while intrans-1,3-diacetoxy-2,2-dimethylindane,

creasing the extent of isomerization of 1,3,7-octatriene to the 1,3,6-isomer. It is recommended that carbon monoxide, if used, be limited to a maximum partial pressure of about 50 atmospheres. The presence of excess arene ligands does not afpurities) in 25 ml of pure cyclohexane and 0.20 g of tricarbonyl(methyl benzate)chromium were placed in a reactor lined with Hastelloy C. The closed reactor was successively cooled in a dry ice bath, evacuated to about 1 mm Hg, warmed to feet the product distribution. 5 room temperature and filled with hydrogen to a few hundred The partial pressure of hydrogen in the process can be in the psig. The reactor was then heated at 200 C. with agitation broad range of about 1 to about 1,000 atmospheres, and is while the hydrogen pressure was raised to and maintained at preferably in the range of about 20 to about 100 atmospheres. 1,200 psig for 6 hours. Flash distillation of the reaction mix- The level of hydrogen pressure has nearly negligible eff t on ture under reduced pressure gave 18 g of product solution. the reaction rate in the preferred pressure range, though lower 10 Gas chromatography it a V8 inch X 25 feet 5 p n levels in this range are slightly favorable to higher 1,6-octanediol succinate column at 78 C. and thermal conductivity tadiene/octene product ratios. detection showed the absence of 1,3,7-octatriene. The major The process is conducted at temperatures in the range of product peaks were at the retention times of 1,5- and 1,6-oc- 25 to 300 C.'When chromium hexacarbonyl is used as the iadienescatalyst, the effective temperatures are referabl in the ran e of 50 to 300 C., and are most preferaltiiy in the i ange of 15%) EXAMPLES 2 42 to 2500 when tricarbonyu afene)chmmium Complexes are These examples were conducted by the procedure of Examused as catalysts, the effective temperatures are preferably in i 1 d h d are presented i T bl 1 Th gas chromato the range of 25 to 250 C., and most preferably in the range of hi d h l ti o ortio in area r nt to 2000 which closely approximate weight percent (of, Purnell Gas The 1,3,7-octatriene, as used in the following examples, can Chr h Joh Wil a d Sons, In 285 1962), be obtained conveniently by the catalytic dimerization of bu- Gas Chromatographic analyses f all products were carried tadiene -i Takahashi at Chem- (Japan), out with the butanediol succinate column described in Exam- 454 )l- The usual impurities Present in triene Produced ple 1. In some instances the products were also analyzed by y route are 1,36-OCtall'iefle and y each of two other columns. When all three columns were cyclohexone j These impurities can b e o ed, but used, the data in Table I are composite results. The two other their separation from 1,3,7-octatriene by distillation is not columns areasfollows: easy. However, since 4-vinylcyclohexene is nearly inert in the a. A /e inch X 15 feet column packed with 80-100 mesh gas process of the invention and can be separated readily from Chrom RA containing 20 percent of ,B, B-ox- 1,5- and 1,6-octadienes by fractional distillation, its presence ydipropionitrile, using thermal conductivity detection. in the reaction mixture is not a disadvantage. In fact, the b. A 50 feet capillary column coated with solid polyphenyl presence of 4-vinylcyclohexene may be desirable because it ether, Using flame ionization detectionappears to inhibit formation of by-product octenes and 00- The Columns f calibrate? f found to have sPmewhat tane. ferent separation characteristics. They all readily separated 1,5-0ctadiene, 1,6-octadiene, 4-vinylcyclohexene and 1,3,7- SPEClFlC EMBODIMENTS OF THEINVENTION octatriene from each other. However, possible contaminants Th f n l t th fth such as the octenes, isomeric octadienes and isomeric oce 0 Owing cxamp e5 l ustra e 8 process e mven tatrienes could not be separated clearly in all instances. An T mcarbonyumethyl benzoatekhromlum. catalyst analysis of their combined capabilities with representative shown in Examples 1-23 was prepared from chromium he samplesindicate the following: acarbonyl and methyl benzoate by the procedure of Nicolls Butanediolsuccinate Column and whining Chem (1959) The pentacarbon' Data are reliable with recognition that the 1,5-octadiene yl( triphenylphosphine)chromium catalyst shown in Examples fraction may contain Lectene and some 4 and 1 7 40412 was Prepared by 3 Procedure analogous to that tadienes, and that the 4-vinylcyclohexene fraction may described for the preparation of corresponding isonitrile com- Contain ly3 octadiene I f d analysis f the Plexes y Murdoch and Henzi, OrganometaL Chem- 5, 166 tadiene fraction shows that the 1,4- and 1,7-isomers are l966)- minor components. I

Composite of all three columns EXAMPLE 1 Data are reliable with recognition that the 1,5-octadiene fraction may contain small amounts of 1,4- and 1,7-oc- A solution of 3.0 ml of 1,3,7-octatriene percent 1,3,7- tadiene and that the 4-vinylcyclohexene fraction may octatricne, with 4-vinylcyclohexene and l,3,6-octatriene im contain 1,3-octadiene.

TABLE I [Ilydrognnnlion (ll 1,3,7-0chttrioim with $()|l1l)l(\ chromium catalysts] lit-tuition llIlXLllI'U Conditions (10 :iiiiilysis 1,3,7()'l 'lump, 'Iiino, Ila/C0 Example Catalyst. -g. Solvent -inl. -inlt 0. hr. p.s.i.g. Col." 1,6-01) 1,6-OD 4V0 II 1,3,7-0'1 2 A-0.20 77%-!) 160 6 300 B DS 11 60 22 2 A-0.20 77%-J 160 6 1,250 COMP 11 d 64 d 22 A-0.20 89%-1 6 13, 000 B DS 11 89 A-0.070 99%-0. 8 6 1, 200 BDS 28 d 47 0 A-0AO 98%-1 140 6 1,200 B D S 6. 8 27 63 A-0.020 89%-3 160 (1 1, 270 BD S 1 2 11 86 A-0.20 99%-2 6 1,200 00 MP 34 54 1 A-0.20 89%-1 150 6 1, 300 B D S 21 G5 10 1 A-0.20 89%-1 6 290 B D S 17 52 10 16 A-0.40 99%-3 6 1, 200 BDS 31. 5 d 60. 4 2 A-0A0 98%-1 165 6 1,200 BDS 30 d 55 9 A-0.20 89%-1 200 6 1, 250 COMP 8. 5 13. 9 1 0. 5 A-0.20 89%-1 150 6 1, 230/25 BDS 11 88 A-().20 89%-1 150 6 1, 300/65 B D S 1 2 13 84 A-0.20 8J%-1 6 1 220/15 BDS 4 11 13 67 A-0.20 89%-1 200 6 1, 300/25 COMP 6. 7 40 14 22 A-0.20 8.J%-1 250 6 1, 000/65 BDS d 43 11 12 A-0.20 ()rIlt2/Ml1-8/0.5 80%-1 160 6 200 BDS 21 63 10 3 A-0.20 lli2/Ml1-8/0.5 80",,-1 200 6 1,300/30 BDS 11 50 10 17 a A-().20 il-(l llu-8.t. 8.l%-l 150 6 1,220 BDS 21 G6 10 2 TABLE I (ontinued lHydrogenation i 1,3,7-0ctatriene with soluble chromium catalysts] Reaction mixture Conditions (3C analysis 1,3,7-01 Temp, Time, Hz/CO b Example Catalyst -g. Solvent -m1. -ml. C. hr. p.s.i.g. Col. 1,5-0D 1,6-01) 41 C11 1,3,7-0T Acetone -8 89%-1 36 6 1, 200 BDS 5 4 12 76 Acetone -8. 89%-1 100 6 1, 200 BDS 24 64 one 7T7 -9 200 6 1,200 COMP 9. 0 56 22 1 d0.. 777 -"J 225 6 1,400 BDS 28 31 12 2 ..do.. i71-9 200 6 245 COMP 9 65 l9 d0 77%-0 200 6 1,300 BDS 16 57 TI 17 CeH1e-8 8'J7;-1 200 6 1,000 BDS 23 56 J l CaH12-8 77%-l 200 6 1. 300 13 DS 13 I 62 1!! l C6H12-8 9!-7;-1 200 6 1.300 COMP 23 65 0. 5 1 6 l2- 89%-1 200 6 1, 300/25 B DS 6 46 11 21 C5H12-8 89%-1 200 G 1,400/100 BDS 6 9 13 56 CiH1:-8. 89%-1 275 6 1, 240/200 Comp 9. 6 33 15 17 Acetone-8 89%-1 80 12 1, 200 13 DS I 5 3 10 80 d0.. 89%-1 150 6 1, 200 CO.\1P 3 70 13 4 CtHi-8 997 -2 130 6 1, 200 COMP 22 5 2 6!) CeH12-8... 99%-2 140 8 1,300 COMP 22 24 1 50 CaH1:-8.. 7T7,,-1 160 6 1,500 COMP 20 40 21 5 CtH1FCeHt-8=L 89%-2 140 8 1,250 COMP 20 3 1'3. 5 62 C5H1z-8 l7%-1 200 6 1,225 COMP 8 51! 22 1.5 CI1H1"-S- 779Z-l 210 6 1,400 C0311 14 52 17 1 CsH z-8 897 -1 225 6 1,300 (I 0M1 17 42 J 2 a The other component is AVCH. b CO pressure, when shown, is the initial pressure at 25 C.

c BDS indicates data from butanediol succinate column only. COMP indicates composite data from three different columns. See text for explanation.

' The materials in these instances were also isolated by Nors.-Abbreviations, .\1B =methyl benzoate; OT octatriene, carbonyl-(methyl benzoate)chromiurn; B chromium hexacarbonyl; chromium.

The 1,5- and 1,60Ctadicncs produced by the process of this invention are useful as comonomers in the preparation of vinyl olymers. Polymers containing the copolymerized dienes can be cured by conventional means such as vulcanization. A particularly valuable use of the dienes is in elastomeric ethylene/propylene/diene copolymers, which are well known in the form of commercial EPR rubbers. In this specific use, 1,5- or 1,6-octadiene can be used in place of 1,4-hexadiene, which is well established as a cure-site-introducing comonomer in EPR elastomers.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Method of making 1,50ctadiene and 1,6-octadiene which comprises contacting at a temperature in the range of 25 to 300 C., 1,3,7-octatriene with hydrogen at a partial pressure of about 1 to 1,000 atmospheres in the presence of a catalytic amount of a catal t consisting of a neutral complex of chromium containing at east three carbonyl ligands joined to each chromium atom.

2. Method of claim 1 in which said catalyst is selected from Cr(CO) Cr(CO) .,PL and Cr(CO) Q wherein each L is alike or different and is a hydrocarbyl group free of aliphatic unsaturation, or an aryl group having up to three substituents consisting of halogen, lower alkoxy and preparative G C and their identities verified by NMR.

OD=octadiene; 4VC11=4-vinylcyclohexene; 1,3,7-0'1 -1.3,7-octatriene; A-tri- C tricarbonyl(benzene) chromium;

D pentacarbon yl(triphenylphosphine) saturated hydrocarbon, said L having up to 10 carbon atoms, and Q is an aromatic compound of up to 14 carbons selected from aromatic hydrocarbons, or such aromatic hydrocarbons having up to three substituents consisting of lower alkoxy lower alkanecarbonyloxy, lower alkoxycarbonyl, lower alkoxycarbonylalkyl, hydroxymethyl, cyano, lower alkylcarbonyl, arylcarbonyl, amino, N-( lower a1ky1)amino, N,N-di(lower alkyl)amino and halogen.

3. Method of claim 2 in which said reaction is conducted at a temperature in the range of C. to about 200 C.

4. Method of claim 2 in which the catalyst is present in an amount of 0.01 to 0.2 grams per ml. 1,3,7-octatriene.

5. Method of claim 2 in which said catalyst is tricarbony1( methyl benzoate )chromium.

6. Method of claim 2 in which said catalyst is tricarbonyl(benzene)chromium.

7. Method of claim 2 in which said catalyst is hexacarbonyl chromium.

8. Method of claim 2 in which said catalyst is pentacarbony1( tn'phenylphosphine )chromium.

9. Method of claim 2 in which reaction is conducted at a temperature in the range of to 250 C.

10. Method of claim 9 in which the catalyst is present in an amount of 0.01 to 0.2 grams per ml. 1,3,7-octatriene.

i i t i i P0405? UNITED STATES PATENT ()FFTCE CERTTFTQATE l li EUTTN Patent NO zr tzljzib w l m-J1. n@ animal...

lnventoflsl Lawrence Wavne (lesser It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Cover page, Abstract,, lines it and 5 "pentacarbonyl( phosphine" should be pentacarbonyl(trisubstituted phos phine)chromium Col. 2, lines A5 and A6, in two instances the words alkyl)amino" occurring after "(lower alkyl)amino" should be deleted;

Col. 6, Table I Example 38, in the column under "1,6-OD" the number "b0" should be M1, and in the column under "1,3,7-0'1", the number "5" should be changed to L --e Signed and sealed this 9th day of January 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

2. Method of claim 1 in which said catalyst is selecteD from Cr(CO)6 Cr(CO)5PL3 and Cr(CO)3Q wherein each L is alike or different and is a hydrocarbyl group free of aliphatic unsaturation, or an aryl group having up to three substituents consisting of halogen, lower alkoxy and saturated hydrocarbon, said L having up to 10 carbon atoms, and Q is an aromatic compound of up to 14 carbons selected from aromatic hydrocarbons, or such aromatic hydrocarbons having up to three substituents consisting of lower alkoxy lower alkanecarbonyloxy, lower alkoxycarbonyl, lower alkoxycarbonylalkyl, hydroxymethyl, cyano, lower alkylcarbonyl, arylcarbonyl, amino, N-(lower alkyl)amino, N,N-di(lower alkyl)amino and halogen.
 3. Method of claim 2 in which said reaction is conducted at a temperature in the range of 100* C. to about 200* C.
 4. Method of claim 2 in which the catalyst is present in an amount of 0.01 to 0.2 grams per ml. 1,3,7-octatriene.
 5. Method of claim 2 in which said catalyst is tricarbonyl(methyl benzoate)chromium.
 6. Method of claim 2 in which said catalyst is tricarbonyl(benzene)chromium.
 7. Method of claim 2 in which said catalyst is hexacarbonyl chromium.
 8. Method of claim 2 in which said catalyst is pentacarbonyl(triphenylphosphine)chromium.
 9. Method of claim 2 in which reaction is conducted at a temperature in the range of 150* to 250* C.
 10. Method of claim 9 in which the catalyst is present in an amount of 0.01 to 0.2 grams per ml. 1,3,7-octatriene. 